There seems to be differing standard for storing %totaltracks%... in ID3v2.4 it is stored in TRCK as "/xx" but for APEv2 it is common to use a seperate tag field TOTALTRACKS. I don't even know how it is handled in Ogg, Matroska or MPEG4...
I think the wizard should adhere to these standards and make it easier for the user to automagically add totaltracks to the tags without breaking stuff for their player software/hardware. So the wizard should automatically choose the standard for adding totaltracks information and even if leading zero is part of the standard or not. Of course, the user should still be able to override this, maybe a simple tick box "use tag's standards" that will grey out the other settings? So it is essential that the wizard changes the settings on a per file/tagformat basis, for a multi-tagformat list of files.
I hope this is good request.
PS: ID3v2.4 way of storing totaldiscs is similar: in TPOS it is "/x", "/xx", which is mapped to DISCNUMBER. This is one example where not only the naming of the tag field (DISC vs. DISCNUMBER) is confusing, but also wher ethere is no actual totaltracks frame in the ID3v2.4, but adding TOTALTRACKS in MP3Tag will create a custom TXXX frame. IMHO the next big feature for MP3Tag could be a wizard that can help users to clean up such mistakes they may have made when tagging? Or maybe highlighting the tag field names in the extended tag editor that correspond to standard ID3v2.4 frames?